1. Field of the Invention
The present invention generally relates to a power source which applies a voltages to a line and a different voltage to another line; in particular, a power source which includes a first power source unit that applies a voltage to a control unit and a second power source unit that applies a different voltage to a unit to be controlled by the control unit; and further, to an image forming apparatus which uses the power source. In addition, the power source can be used in many apparatuses, such as a scanner, a printer, a copying machine, a facsimile, a computer, and so on.
2. Description of the Related Art
In Patent Document 1, an image forming apparatus is disclosed. In the image forming apparatus, when an interlock switch disposed at the output side of a power source which outputs a control voltage of 5 V and a load driving voltage of 24 V is turned off (non-conductive), a load connecting to the 24 volt line is turned on (conductive) in response to OFF of the interlock switch, and a capacitor having a large capacity on the 24 V power line is discharged via the load. With this, protective control at an interlock time is established.
In Patent Document 2, a power source and an image forming apparatus are disclosed. The power source is a DC power source for outputting plural voltages. In the power source, a relay coil is connected to an output line of one power source in plural power sources outputting different voltages via an interlock switch and a relay contact is connected to an output line of another power source.
In Patent Document 3, a power source and an image forming apparatus are disclosed. The power source includes plural power sources outputting different voltages and a signal processing device that stops a power output of each of the power sources in an order storing in a memory when a power switch is turned off.
As a power source voltage applied to electrical units in electrical apparatuses, an OA (office automation) apparatus, and a FA (factory automation) apparatus such as a copying machine, a printer, and a facsimile, various voltages such as 3 V, 5 V, 12 V, 15 V, and 24 V are used. Each of these power source voltages is used in detection of various signals, operations for various actuators and motors, and control for the actuators and the motors. As the power source voltage for the detection and the control, 3 V or 5 V is used. In addition, as the power source voltage for various operations of the actuators, the motors, and other loads, 12 V or 24 V is used.
When the power control does not work normally in these apparatuses, the supply of power to the various loads becomes uncertain, and in some cases, a switching device for supplying the power is broken; further, the apparatus may be broken by a wrong power supply. As reasons why the power control does not work normally, it is considered that they include a runaway CPU and a proper voltage not being applied to power control.
For the runaway CPU, a watchdog timer is disposed, or plural CPUs monitor each other's operations, and when an abnormal operation is detected, a reset signal is generated. From a view point that a proper voltage is applied to the power control, in a steady state after each voltage rise, a voltage in a proper voltage range is supplied and there may be no problem.
[Patent Document 1] Japanese Laid-Open Patent Application No. 9-297507 (Japanese Patent No. 3484013)
[Patent Document 2] Japanese Laid-Open Patent Application No. 2002-345148
[Patent Document 3] Japanese Laid-Open Patent Application No. 2002-354793
However, conventionally, at a rising time or a falling time of power, a sequence or the order of outputting voltages is not set. That is, a sequence in which a control voltage is output with priority is not set. In a power source which outputs many voltages or has many power source units, a sequence, which outputs the control voltage with priority in the power control before outputting other voltages at a rising time of the power source, has not been set. Further, a sequence, which holds the control voltage and stops other voltages before stopping the control voltage at a falling time of the power source, has not been set. That is, the above sequences have not been set in the power source.